Three Ukrainian diplomatic missions have received threatening letters soaked in red liquid, Interfax Ukraine cited a senior official as saying on Thursday, a day after a letter bomb exploded at the country's embassy in Spain.
Foreign Minister Dmytro Kuleba said the incidents were an attempt to intimidate Ukrainian diplomats, the agency reported.
"If they have already started attacking embassies... it means that they are afraid of us, they are trying to stop us," it quoted him as telling national television.
"Inside these letters was a symbolic threat to Ukraine... all the envelopes were soaked in red liquid at the time they were received," he said, declining to give further details.
Continued threats by mail
A package addressed to the Ukrainian ambassador to Spain detonated at the embassy in Madrid on Wednesday as a security official investigated it, causing him to suffer minor injuries.
Ukraine's ambassador to Spain, Serhii Pohoreltsev, appeared to blame Russia in comments after the blast.
Russia invaded Ukraine nine months ago in what it calls a "special military operation" that Kyiv and the West describe as an unprovoked, imperialist land grab.
Spain has sent or committed to send military and humanitarian equipment to support Ukraine in the war.